import java.util.*;
public class TestMain {
	public static void main(String[] args)
	{
		Scanner read = new Scanner(System.in);
		int n = read.nextInt();
		
		int[] dp = new int [n+1];
		for(int i=0; i<n+1; ++i)
		{
			dp[i] = 0;
		}
		dp[1] = 1;
		
		for(int i=2; i<n+1; ++i)
		{
			dp[i] = dp[i-1] + dp[i-2];
		}
		System.out.println(dp[n]);
	}

}
